


Final Destination

by hanwritesstuff (hannahkannao)



Series: tumblr drabbles [1]
Category: Haikyuu!!
Genre: Canon Compliant, Gen, M/M, chemistry is hard, sort of fluffy i guess??
Language: English
Status: Completed
Published: 2016-02-28
Updated: 2016-02-28
Packaged: 2018-05-23 15:42:54
Rating: General Audiences
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 1,169
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/6121336
Author URL: https://archiveofourown.org/users/hannahkannao/pseuds/hanwritesstuff
Summary: <blockquote class="userstuff">
              <p>Yamaguchi says he can't do double replacement reactions.</p><p>Tsukishima says he can't use a simile correctly.</p><p>Neither of them are correct in their assumptions.</p>
            </blockquote>





	Final Destination

**Author's Note:**

> Prompt #37 from [this post](http://violinist-tsukki.tumblr.com/post/138445882006/send-me-a-pairing-a-number): "I won't leave you behind" (for @grumpyroosters on tumblr!)
> 
> I took chemistry last year and I didn't remember any of this so I had to look it all up again :')

Finals. The bane of every student’s existence and the cause of enough unnecessary stress to last the rest of the year. With the excess work that traditionally came with the end of the term, grades were holding onto the edge of a benchmark, gradually losing their hold and about to slip. This was the chance to either get them back up or guarantee their ultimate fall.

And Yamaguchi Tadashi still couldn’t get double-replacement reactions down.

He’d been in chemistry long enough, and he _knew_ reaction equations were important for labs and whatnot, and he knew that besides all the exceptions, the rules were extremely simple, but he just couldn’t understand it. He knew what elements the symbols on the worksheet stood for - he would have known even if he didn’t have the periodic table next to him - but he couldn’t put them together and mix them around.

He sighed, laying his forehead down on the desk. He knew he should have gone in and asked his teacher about it earlier instead of trying to understand it on his own.

“Is it chemistry again?” Tsukishima asked, presumably sitting on top of Yamaguchi’s bed like he had been the entire time.

“What else could it be?” Yamaguchi slowly sat up again, realizing with dread that even after resting his forehead on the cool wood of the desk for a few seconds, nothing had changed in regards to what he understood of the equations on his worksheet. “You know it’s my worst class.”

“At least you’re stuck on questions that actually have concrete answers.” Tsukishima narrowed his eyes at the piece of paper in his hands as Yamaguchi spun around in the desk chair. “I don’t know how the language arts final’s even going to work.”

“It isn’t going to be that bad, Tsukki.” Yamaguchi reached down to grab a piece of paper out of his bag. “It’s just going to be on the vocabulary and stuff.”

“The vocab isn’t really what I’m worried about.”

“Is it the essay?” Yamaguchi asked. “Because that’s just a normal essay.” He paused. “Wait, is it the poetry?”

“Maybe.”

“Don’t worry, it doesn’t have to be good poetry.” Yamaguchi giggled. “Mine is going to suck. But as long as you use all the devices correctly, you’ll get the points.”

“Yeah, but it’s still going to be a crappy poem.” Tsukishima frowned.

“I’ll help you, if you want.” Yamaguchi smiled. “If you help me with chemistry.”

“Deal.” Tsukishima scooted over on the bed, making enough space for Yamaguchi to sit down next to him. “Is it just double replacement you’re worried about?”

“I guess.” Yamaguchi shrugged.

“Okay.” Tsukishima frowned. “So basically, in every compound, there’s going to be two ions, a cation and an anion. The cation’s positive and the anion’s negative, and in the notation for the compound, the cation comes first.”

“Right.” Yamaguchi nodded. “I got that much.”

“So in a double replacement reaction, you have two compounds, and when they react, the cations switch places,” Tsukishima said, “I mean, you can technically say that the anions switch instead, but it’s the same thing either way. Like if you have one compound AB, and another compound CD, with A and C as the cations and B and D as the anions, after the reaction, AB plus CD becomes CB plus AD, right?”

“Yeah,” Yamaguchi said, “I get that part, it’s just everything else that’s confusing.”

“Okay.” Tsukishima looked over at the worksheet Yamaguchi was holding. “Can I have that for a second?”

“Yeah.” Yamaguchi handed it over, slightly ashamed that he only had half of it done.

“Okay.” Tsukishima looked at it with narrowed eyes before looking up again. “Let’s do number six, it’s a lot easier doing it than trying to explain it.”

“Okay.” When Yamaguchi looked down, he saw that number six was the first one on the worksheet he hadn’t done. NaCl + H₂SO₄. Sodium chloride and hydrogen sulfate. The beginning didn’t look so bad. He just knew that the worst was coming

“So first off, we have to figure out the other side of the equation and balance it.” Tsukishima leaned over to grab a pencil from next to him. “You’re better at this part than I am, it shouldn’t be that hard.”

“Okay.” Yamaguchi nodded, looking at the formula in front of him. He knew from all the practice he’d had that sodium and chlorine both had a charge of one, as did hydrogen. Sulfate was the only one that had a charge of two. After that, he found that switching them around wasn’t that bad. The products were sodium sulfate and hydrochloric acid, Na₂SO₄ + HCl.

“See? You’re good at this,” Tsukishima said, narrowing his eyes at the paper. “Having trouble remembering the solubility rules or what?”

So that’s what those were called.

“Yeah.” Yamaguchi grinned sheepishly as he tried to remember what they were. No matter how hard he tried, he could only remember that there were eight of them. “Sorry.”

“No, they’re complicated.” Tsukishima frowned. “There isn’t really a mnemonic or anything, so you kind of just have to remember them for what they are.”

Great.

“The first rule is that all of the alkali metals are soluble.” Tsukishima got on his knees and reached over right in front of Yamaguchi to grab a piece of paper. “Like everything in the first column of the periodic table.” He paused for a second, jotting something down on the piece of paper. “The second rule is -”

“Wait up, I have to write this down!” Yamaguchi frantically tried to write it down, but sighed upon finding that he couldn’t read his own handwriting when he was writing so fast. He knew he’d had a worksheet on it, but he must have lost it, since he couldn’t find it anywhere.

“Don’t worry about it.” Tsukishima held up the piece of paper he’d been writing on, which had the rule written in his typical impossibly neat handwriting. “I won’t leave you behind.”

Yamaguchi’s sigh of discouragement turned into one of relief as the corners of his mouth turned up into a smile. “Thank you!”

“No problem. It’s easier for me to memorize things if I write them down a lot, anyway.” Tsukishima shrugged. “I’ll explain them as I go, then I’ll give this to you at the end.”

“You didn’t have to do that.”

“I’m just going off the impression that you’re going to have to spend an hour teaching me how to write decent poetry.” Tsukishima smirked. “This is nothing.”

Yamaguchi laughed, looking back at the chemistry worksheet in his hand. “I don’t know if I can do _that_ , Tsukki.”

“Please." Tsukishima scoffed. "I can’t even use a simile correctly. It’s like me trying to flirt, it just doesn’t work.”

Yamaguchi’s eyes widened, not quite sure what he was getting at. “Um, well, you just did. Use a simile correctly, I mean.”

Tsukishima paused for a second before he looked back down at the piece of paper written on it. “Huh.”

**Author's Note:**

> On tumblr at either [hanwritesstuff](http://hanwritesstuff.tumblr.com) or [violinist-tsukki](http://violinist-tsukki.tumblr.com)!
> 
> Thanks for reading! <3


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